STMicroelectronics L4902A

Overview

L4902A from STMicroelectronics is a monolithic dual low-dropout 5V linear regulator IC with integrated reset generator and output disable control, designed for microprocessor system power management. It delivers two independent 300 mA regulated 5 V ±2% outputs, features input overvoltage protection up to 60 V, active discharge on Output 2, and programmable reset delay via external capacitor. It is used in battery-backed CMOS microcomputer systems requiring persistent RAM supply and controlled power-down sequencing.

For engineers reviewing the L4902A datasheet, L4902A pinout, L4902A application, or L4902A equivalent, key selection considerations include dual-output sequencing behavior, reset timing dependency on external capacitance, disable threshold voltage (1.25–2.4 V), output leakage (<1 µA at Output 1), and thermal shutdown with SOA-protected pass transistors.

Technical Context

The L4902A integrates two independent LDO regulators sharing a common input and ground, where Output 1 remains active under all conditions while Output 2 is enabled only when Input > VIT (≈V01 + 1.2 V) and Output 1 > VRT (≈V02 − 0.15 V). The reset output is asserted high after a programmable delay (t_RD = C_t × 5 V / 10 µA) once Output 2 turns on.

Output 2 is disabled by a logic-high signal (>V_DT) on Pin 3, causing internal switching and active discharge of its output capacitor. Reset assertion is synchronized to Output 2 state and referenced to Output 2 voltage, with hysteresis (30–80 mV) on both reset and input thresholds to prevent chatter during brown-out transitions.

Key Specifications

Pinout & Package

Package: Heptawatt vertical (7-pin single-in-line, SIP), thermally enhanced with R_{th j-case} = 4 °C/W, suitable for through-hole mounting on industrial PCBs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-regulator-with-reset applications.

Compared with MAX692A and TPS767D318, the L4902A uniquely combines dual 5 V LDOs, capacitor-programmable reset, active Output 2 discharge, and sub-µA Output 1 leakage-making it irreplaceable for legacy battery-backed µP systems requiring deterministic power-loss response.

Availability

L4902A is available at Aetrix Electronics and suitable for CMOS microcomputer power management, shadow-RAM data preservation, keyboard-controlled standby systems, and watchdog-enabled recovery circuits requiring stable component supply across extended industrial lifecycles.

Supply support for L4902A includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The L4902A belongs to ST's legacy linear regulator product line, engineered specifically for robust, low-complexity power sequencing in battery-backed microprocessor systems operating in harsh electrical environments.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4902A supports continuous DC input up to 28 V, with transient overvoltage tolerance up to 60 V for durations ≤40 ms. Operation above 28 V requires verification of thermal dissipation given output loading and ambient conditions, as junction temperature must remain below 150°C. The device includes internal SOA protection and thermal shutdown to prevent damage during overload.

How does the reset output behave during input brown-out?

The reset output goes low when Output 2 is disabled-either due to input voltage dropping below V_IT (≈V₀₁ + 1.2 V), Output 1 falling below V_RT (≈V₀₂ − 0.15 V), or a high signal on the Disable pin. Hysteresis (250 mV on input, 30–80 mV on reset threshold) prevents oscillation during slow voltage transitions, ensuring clean, glitch-free reset assertion and deassertion.

Can Output 1 and Output 2 be used with different output capacitors?

Yes-Output 1 requires ≥10 µF low-ESR capacitor for stability and low-leakage retention; Output 2 uses ≥22 µF with active discharge support. The datasheet specifies minimum values and ESR ranges per output, and mixing capacitor types (e.g., tantalum on Output 1, ceramic on Output 2) is permitted as long as each meets its respective stability criteria and ripple current rating.

Is the L4902A still in production or considered obsolete?

The L4902A is marked "Obsolete Product(s)" in its official STMicroelectronics datasheet revision (June 2000), indicating formal discontinuation. However, Aetrix Electronics maintains legacy inventory with full traceability and offers lifecycle coordination support-including last-time-buy planning, cross-reference guidance, and engineering consultation for migration paths where functional replacement is required.